[Richard]

I have installed the vinyl planking similar to what you described in the front salon with HWH slide.

I glued it down.

I used a high end backing underneath which has a little sponginess to it. I don't like the fact the floor gives when I step up on it. It's most noticeable with the slide out when you weight the sections between the fixed floor and the slide out floor.

Play with the positioning of the plank on the side out floor. You will find the floor does not raise straight up and down, but rather the side closest to the street comes up, and then the side closest to the interior of the coach pivots about a hinge point on the street side. This is important because if you just install a plank flush with the interior edge of the floor, it will hang when the floor pivots up. The solution is pretty easy. Through trial and error, position the plank on the slide floor until it doesn't hang on the up swing. It will be about 2 or 3 mm back from the edge depending on the thickness of your plank. Then. position the edge of the plank on the fixed floor with a slight overhang to help close the gap.

I made an error and tried to make my gaps about 1/32, cause I'm OCD like that. You will be better off with a 3/32 to 1/8 gap.

Post a picture of your streetside couch. Depending on it's setup you may or may not have one additional challenge of getting the floor to slip under the couch end columns when the slide comes all the way in.

What I am really trying to say is that there are a few watchouts, but it can be made to work. It is best to use some of your planking and other materials to make mockups at the slide floor interface, and the fixed floor where the slide comes in and over it. The mockups and a little figuring will show you what critical dimensions you have for thickness and location of seams.